The present invention relates generally to the ventilation of the storage environment for bulk-stored food grains, and more particularly to ventilation systems which force air through stored grain.
In the field of bulk storage of grain, it has been found useful to ventilate the stored grain in order to bring the grain to and keep the grain in a state of dormancy, a process more fully described in U.S. Pat. No. 4,045,878. One common type of grain storage bin used in this process is constructed with an empty chamber (plenum) below the grain bin. The top of the plenum, which is the bottom of the bin, ordinarily is perforated so that fans can blow air into the plenum thereby forcing the air upwardly through the grain and out a vent in the top of the bin. The prior art of U.S. Pat. No. 4,045,878 teaches that fans may be placed near the vent in the free space between the roof of the bin and the top of the grain to aid in the air circulation within the bin. The problem encountered with the prior art, however, is that as the grain depth increases, resistence to the flow of air increases. When the air resistance reaches a certain level, generally three inches static pressure (displacement of water column), occuring when grain depths are approximately 14 feet, the horsepower requirement of the plenum fans for achieving an adequate ventilation rate through the stored grain becomes prohibitive. In general, commercial grain storage bins are often filled in excess of 14 feet and consequently are not amenable to adequate ventilation and to maintaining the stored grain in an equilibrium state with the atmospheric air temperature and moisture level.